As electronic apparatuses, such as mobile telephones, have rapidly having small overall sizes and low power consumption, components for constructing various circuits in the apparatuses have low withstand voltages. As the result, the electronic apparatuses have more troubles, such as breakdown of the electronic components, particularly semiconductor devices, which is caused by static pulses generated when conductive parts in the electronic apparatuses contact a human body.
A light emitting diode, a semiconductor device or an electronic component, is widely used as a back light of a display or as a flash light of a small camera. Such a light emitting diode, however, has a low withstand voltage.
In order to protect the light emitting diode, a varistor connected between a ground and a line having static pulses entering thereto for bypassing the static pulses to the ground, thus preventing a high voltage from being applied to the diode.
FIG. 24 is a cross-sectional view of a conventional multilayer chip varistor 105 disclosed in Japanese Patent Laid-Open Publication No. 8-31616. Multilayer chip varistors have small overall sizes and are often used in small electronic apparatuses. The multilayer chip varistor 105 includes a varistor layer 102 having internal electrodes 100 and terminals 103 connected to the internal electrodes 100 at both ends of the varistor layer 102. Protective layers 104 are provided on upper and lower surfaces of the varistor layer 102.
Varistor layer 102 has a certain thickness enough to have a physical strength avoiding breakage and chipping, and accordingly, prevents the varistor 105 from having a small thickness. For example, the multilayer chip varistor, upon having a length of 1.25 mm and a width of 2.0 mm, has a thickness not smaller than 0.5 mm, thus being prevented from a small thickness. Even if having a predetermined mechanical strength, a thinner varistor allows bismuth oxide, a component of the varistor layer 102, more to evaporate during a baking process, accordingly having varistor characteristics and reliability of the varistor deteriorate.